Low-Hysteresis and Lineear Piezoelectric Actuator made from Ultra-fine Particles

点击翻译按钮获取中文摘要

Crystals generally show different characteristics from bulk crystals when their sizes become an order of nanometer. We have been studying this 'size effect' in ferroelectric fine particles for several years and found that the crystal size affects the domain wall movements or the crystallizing process,which establishes a method to synthesize ultra-fine particles. In the present work, we have attempted to improve the hysteresis phenomena or the non-linearity appeared in the relation between the displacement and the applied voltage in piezoelectric PZT actuators. Lead, titanium, and zirconium alkoxides are dissolved in an organic solvent. Hydrolyzing the solution gives PZT fine particles which are still in amorphous state. The amorphous fine particles can be crystallized through the heating at 600ﾟC in air for 5h. The crystallizing temperature is much lower than that of bulk crystals(1280 ﾟC). The lowered temperature enables to obtain ceramics of stoichiometric composition because lead does not evaporate at this temperature. Fine particles obtained are calcined through HIP(hot isostatic pressing) to form a ceramic disc. The ceramic form fine-particles shows quite small hysteresis of an order of 1%, much less than that of conventional ceramics(about 10 %). A typical size of the small particles composing our ceramics is found to be several hundreds nanometers by SEM observation. The size is not still enough small, however, to inhibit the domain wall movement. High resolution TEM observations suggest that fine structures of several nanometers exist in the particles. Thus, the fine structure seems to be 'traces' of boundary of starting powders and should act as pinning points of the wall movement.